Sharif Digital Repository

The strategies of Inherently Safer Design (ISD) provide a conceptual approach in order to design equipment and processes with substantially improved safety level. However, this may lead to a less economically attractive design. This study aimed to obtain optimal decision parameters of a reactor network system to produce allyl chloride. The objective functions were the risk level, including the severity and the frequency of the accidents, which were associated with the hazards in the network and the economic profit of the process. Based on this optimization approach, an array of optimal solutions (called Pareto front) was obtained as a trade-off between the objectives under investigation. A... 

Despite the numerous researches in Stress Corrosion Cracking (SCC) risk of austenitic stainless steels in aqueous chloride solution, no formulation or reliable method for prediction of time to failure as a result of SCC has yet been defined. In this paper, the capability of artificial neural network for estimation of the time to failure for SCC of 304 stainless steel in aqueous chloride solution together with sensitivity analysis has been expressed. The output results showed that artificial neural network can predict the time to failure for about 74% of the variance of SCC experimental data. Furthermore, the sensitivity analysis also demonstrated the effects of input parameters (Temperature,... 

Skeletal muscle tissue engineering aims to fabricate tissue constructs to replace or restore diseased or injured skeletal muscle tissues in the body. Several biomaterials and microscale technologies have been used in muscle tissue engineering. However, it is still challenging to mimic the function and structure of the native muscle tissues. Three-dimensional (3D) bioprinting is a powerful tool to mimic the hierarchical structure of native tissues. Here, 3D bioprinting was used to fabricate tissue constructs using gelatin methacryloyl (GelMA)-alginate bioinks. Mechanical and rheological properties of GelMA-alginate hydrogels were characterized. C2C12 myoblasts at the density 8 × 106 cells/mL... 

FAPbI3 perovskites are excellent candidates for fabrication of perovskite solar cells (PSCs) with high efficiency and stability. However, these perovskites exhibit phase instability problem at room temperature. In this work, to address this challenge we use methylammonium chloride (MACl) as an additive and employed a layer-by-layer thermal evaporation technique to fabricate high-quality perovskite films on a large scale of 25 cm2. The optimized perovskite films show high crystallinity with large grains in the μm-range and reveals phase stability due to the presence of MACl after the annealing process. Finally, we achieved PSCs with 17.7% and 15.9% for active areas of 0.1 cm2 and 0.8 cm2,... 

The transformation of gibbsite to α-alumina occurs in the range 1100 to 1300°C. The higher the calcination temperature, the larger the crystallites and this leads to abnormal grain growth. The main goal of this research was to reduce the transformation temperature of gibbsite to α-alumina by reducing the gibbsite particles size. The sodium content of the gibbsite used in the study was reduced to less than 0.1% by washing it in HCl solution. It was then ground in a fast mill at ambient conditions for different times then calcined at different temperatures. The microstructure, particles size and thermal behaviour of the samples were examined with SEM, XRD, XRF, PSA and STA, respectively. In a... 

Gold-catalyzed cyclization of 1,5-diynes with ketones as reagents and solvent provides diversely substituted vinyl ethers under mild conditions. The regioselectivity of such gold-catalyzed cyclizations is usually controlled by the scaffold of the diyne. Herein, we report the first solvent-controlled switching of regioselectivity from a 6-endo-dig- to 5-endo-dig-cyclization in these transformations, providing fulvene derivatives. With respect to the functional-group tolerance, aryl fluorides, chlorides, bromides, and ethers are tolerated. Furthermore, the mechanism and selectivity are put to scrutiny by experimental studies and a thermodynamic analysis of the product. Additionally,... 

The early stages of nucleation and growth of nanostructures can control the shape and final size of the fabricated nanostructure. Therefore, the study of the nucleation and growth mechanism of nanostructures is of great importance. The purpose of this study is to investigate the nucleation and growth mechanism of nickel nanocones from a chloride-based bath containing ethylene ammonium dichloride as a crystal modifier. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry tests were employed to investigate the nucleation and growth mechanism and also the mechanism of crystal modifier performance on the growth of nanocones. Electrochemical studies revealed... 

A new gelator based of oleylamide has been introduced, which was gelled nonpolar hydrocarbon and CCl4 solvents through self-assembly. Also, the gelator formed a two-component hydrogel in combination with SDS, an anionic surfactant. UV-Vis studies revealed that the H-type and J-type aggregation of organogels in hexane and hydrogel in water, respectively. The xerogel, obtained by evaporating the solvent of organogel, selectively gelled and adsorbed oil spills on water surfaces. The effect of the various parameters, including temperature, water acidity and pH on the oil spill adsorption was studied, revealing the high ability of the xerogel to removing the oil contamination from water in up to... 

A multi-residue method using gas chromatography coupled with flame ionisation detector has been developed for simultaneous determination of 10 pesticides in milk. The methodology involved a sample clean-up procedure using ‘quick, easy, cheap, effective, rugged and safe’ followed by a preconcentration step based on dispersive liquid–liquid microextraction. In this regard, acetonitrile was added to the milk sample with specific pH and ionic strength, and the mixture was rigorously shaken. The extracts were centrifuged; then, the organic phase (acetonitrile) was transferred to a test tube and was mixed with deionised water. The mixture was sonicated and chloroform was added as an acceptor phase... 

Understanding the roles of asphaltene and resin as natural surfactants existed in crude oil can enlighten contradicting reported results regarding interfacial tension (IFT) of crude oil/aqueous solution as a function of salinity and ion type. In this way, this study is aimed to investigate the effect of these natural surface active agents on IFT of with special focus on SO42− anion and Mg2+ cation. Two different synthetic oil solutions of 8 wt% of the extracted asphaltene and resin dissolved in toluene are prepared, and then IFT values are measured. After that, the obtained results are compared with the IFT of intact crude oil in contact with the same saline solutions examined in the... 

A critical state model is described within the framework of infinite surface bounding surface/kinematic hardening plasticity. The model can account for both initial anisotropy developing during sample preparation and subsequent evolution of anisotropy in samples along anisotropic loading paths. This model is then used to simulate the anisotropic behaviour of Hostun sand observed in series of stress probing tests conducted in a true triaxial apparatus within a single deviatoric stress plane in stress space. The selection of constitutive parameters for the model is discussed and the model evaluated. Deviatoric stress response envelopes are used to show the deviatoric strains generated in... 

The IP Lookup Process is a key bottleneck in routing due to the increase in routing table size, increasing traffic and migration to IPv6 addresses. The IP routing lookup involves computation of the Longest Prefix Matching for which existing solutions, such as BSD Radix Tries, scale poorly when traffic in the router increases or when employed for IPv6 address lookups. In this paper, we describe a CREW PRAM multiprocessor organization lookup that uses P processor for solving LPM problem. By this technique P-1 IP addresses can be looked up simultaneously thus the performance of processors increase in linear manner. First we categorize all prefixes in some groups based on their first two bytes... 

Until now, many algorithms have been introduced for finding arbitrary shaped clusters, but none of these algorithms is able to identify all sorts of cluster shapes and structures that are encountered in practice. Furthermore, the time complexity of the existing algorithms is usually high and applying them on large dataseis is time-consuming. In this paper, a novel fast clustering algorithm is proposed. This algorithm distinguishes clusters of different shapes using a twostage clustering approach. In the first stage, the data points are grouped into a relatively large number of fuzzy ellipsoidal sub-clusters. Then, connections between sub-clusters are established according to the Bhatiacharya... 

The radiation loss in the whispering gallery resonators causes the eigenvalues of the Maxwell equations with the corresponding boundary conditions complex. The corresponding operators are nonhermitian and for these operators the standard perturbation techniques have some difficulties. In this paper by employing the Floquet theorem a new technique for the φ periodic perturbations is developed. The method is applied to obtain the change of resonance frequencies and losses of φ -perturbed microresonators with cylindrical symmetry. The results are compatible with that are obtained by the Volume Current Method  

Active Queue Management (AQM) policies provide an early indication of incipient congestion to the source. In this paper, we propose a new AQM policy that predicts the instantaneous queue length at the next time instant using adaptive filtering technique. To use this algorithm in fast routers, we have reduced its computational complexity. The proposed method uses a simple linear function as adaptive rule. We show that this adaptive congestion control method is able to control the oscillations in the instantaneous queue length. We compare the performance of our method with the other well-known AQM methods such as RED and PI which are also simulated by MATLAB. We also compare the computational... 

Taxonomy learning is one of the major steps in ontology learning process. Manual construction of taxonomies is a time-consuming and cumbersome task. Recently many researchers have focused on automatic taxonomy learning, but still quality of generated taxonomies is not satisfactory. In this paper we have proposed a new compound similarity measure. This measure is based on both knowledge poor and knowledge rich approaches to find word similarity. We also used Machine Learning Technique (Neural Network model) for combination of several similarity methods. We have compared our method with simple syntactic similarity measure. Our measure considerably improves the precision and recall of automatic... 

Double talk detector is the essential part of an echo canceller to keep the adaptive filter from divergence in presence of near-end speech. This work is a contribution to propose a new double talk algorithm based on power, this method detects double-talk quickly; also it can distinguish the double-talking when the channel has the varying gain. In this paper, we first present an analytical discussion describing this new method and then we show the simulation result to compare our proposed algorithm in both performance and complexity with Giegel algorithm-the most successful one in line echo cancellers. ©2007 IEEE  

Tolyltriazole (TTA) is a well-defined corrosion inhibitor for copper and copper alloys. However, there is little literature about its corrosion inhibition performance for mild steels in corrosive environments. This paper studied the electrochemical behavior of TTA in 0.5 M HCl solutions. Also, the morphology and nature of TTA layers on the steel surface were investigated. Electrochemical results showed that TTA is an excellent corrosion inhibitor for mild steel in acidic media with an efficiency of 91% for 0.07 M concentration. The results also indicated that TTA is a mixed-type inhibitor. XRD analysis revealed that the inhibition mechanism of TTA is based on the formation of an organic film... 

An experimental and modeling study on the feasibility of the Scheibel extraction column is presented for heavy metal separation from chloride solution. In continuous experiments, the chemical reaction systems are considered zinc extraction by D2EHPA and stripping from the loaded organic phase by chloride solutions. The experimental results represent that the best extraction and stripping rates in the agitation speed of 155 rpm and the rate of inlet phases of 28 L/h are equal to 99.56% and 98.11%, respectively. The mass transfer modeling by applying the forward mixing is interpreted for solvent extraction systems in this column with the fitting technique. The calculated results from... 

Three-dimensional macroporous fluorine-doped tin oxide (p-FTO) films were successfully deposited using commercial ink of FTO powder and SnCl2 salt via Dr. Blade method. Various features of p-FTO thin films were studied as a function of the ink composition and sintering temperature. The morphological studies corroborated formation of porous, uniform, and crack-free FTO films after annealing at 300 °C for 10 min in air. X-ray diffraction pattern demonstrated development of highly crystalline FTO films. The lowest sheet resistance of 47 Ω/□ was obtained for the p-FTO film with a thickness of 21 μm. The capacitance of thin p-FTO films was investigated using a three-electrode system and the...